Human skin is covered with the stratum corneum, which is a thin biological protective membrane. This stratum corneum exposed to the external world allows us to live in the dry atmosphere without losing water. The stratum corneum is thin and supple, and contributes to maintenance of healthy skin by preventing loss of body water. Healthy skin is generally said to have a water content of 10 to 20%.
However, aging, change of seasons, etc. may impair normal system for controlling the water content in the stratum corneum, causing rough skin or serious skin problems. Conventionally, an external moisturizer containing polyhydric alcohols such as glycerol, hyaluronic acid, chondroitin, collagen, a mucopolysaccharide, etc. for improving the water retention capacity of the stratum corneum and preventing rough skin has been known (see JP-A No. 2001-89381, JP-A No. 2002-145753 and JP-A No. 2005-314402). Also, an external moisturizer containing β-glucan and heat-treated cells of Enterococcus faecalis in combination has been known (see JP-A No. 2004-269408). In addition, a beauty food containing ceramide and viable cells of lactobacillus in combination has been known (see JP-A No. 2004-254632).